Timing circuit



Dec. 16, 1952 J, w

TIMING CIRCUIT Filed Feb. 26, 1951 VVVVV HQSHQ QNQHEMZOU INVENTOR.

BY Jomu W 5M7" ATTORNEY Patented Dec. 16, 1952 TIMING CIRCUIT.lohn'MCSmjth, Cedar Rapids, Iowa, assignorto Collins iRia-dio; Company,Cedar Rapids, Iowa,

a corporation of Iowa Application-February 26, 1951, Serial No. 212327"4" Claims.

invention relates ln'general tQ-timingcircuits and in'particulartocontrolapparatus-which has arelease time different fronr theconnecttime; Y 1

It becomes desirable-at times to control apparatus "suchthat-'thestarting time-doesnot equal the releasing time. For example, itmay-be-de sirableto energize a relay instantaneously upon the closing ofa switch and have it remainenergized fora predetermined time "afterthe'switch is opened. With this arrangement after the---re lay hasoncebeen energized, avery short interruption of the actuating switch willnot cause the relay. to drop out. Many other applications existwherein'this type of controlis desired.

It is an object of this invention, therefore; to provide an apparatuswhich has a differential between the energization and the deenergizationtimes.

Another object of this invention is to provide an improved timing devicewhich minimizes the load on the electronvalves of the apparatus.

Still another object of this invention is to provide an improved fastacting controlcircuit.

A feature of this invention is found in the provision for a pair ofelectron valves which are connected such that the closing of a controlswitch causes. instantaneous operation of the controlled device .and'the opening ,oftheswitch causes ,dis-

engagement of the controlled apparatus after a The figure illustrates acircuit of this invention.

With reference to the drawing, a first electron valve V1 has its plateI0 connected in series with a controlled device I I to a positive directcurrent voltage. The control device might be, for example, a currentsensitive relay with its actuating coil connected in series between theplate I O'and the positive voltage. The cathode I2 of valve V1 isconnected in series with a resistor R1 to ground.

A second electron valve V2 has its plate I 3 connected to ground and itscathode I4 is connected to the grid I 6 of valve V1. A condenser C isconnected between the cathode I4 and ground.

The grid I I of valve V2 is connected to a resistor R2 which has itsopposite side connected to the cathode I4. The grid I! is also connectedto th junction of a pair of resistors, R3 and R1.

The opposite side of R3 is connected to a negative direct currentvoltage and the opposite side of resistor R4 is connected to ground. Aswitch 2 S1 hasone side connected to ground and a-tenninal I8 isconnected to-the grid-I1; so thatthegrid may be connected anddisconnected to ground whenthe switch S1 is closed and opened," respectively.

The values of components might be:

R1 ohms R do 1,000,000 B3 a. .dO; 100,000 R4 do 100,000 C microfarad 1.

The positive voltageconnectedito the-platelO- through the control deviceI] is 25.0 voltsdirect current. The negative voltage connected to R11540 volts direct current.

In operation, suppose thatswitch S1 has been open for a. relativelylongtime. Then the. volt.-

minimum current andthe grid II andcathoderl l will'beat substantiallythe same potential... In this. condition the control device It will haveminimum current. passing through it andl will therefore. b.e;unactuated.

Assume that switch Srisclosed. The grid. Il-f of.

tube V2 is immediately connected to ground potential thus becomingpositive relative to the cathode I4. This causes the tube V: to act as adiode thus very quickly discharging the condenser C to ground potential.The grid l6 of tube V1 is connected to the condenser C and thus itsvoltage rapidly goes to ground potential thus allowing the currentthrough tube V to increase almost instantaneously when switch S1 isclosed. The controlled device I I is actuated. Tube V1 will continue toconduct as long as the switch S1 is closed.

Assume that the switch S1 has just been opened. The tube V2 wil1immediately be cut off or have minimum current for the reason that thenegative control voltage connected to R3 will immediately cause E2 tobecome negative. The tube V1, however, will continue to conduct untilthe condenser C has charged sufiiciently to cut it oil. The timeconstant for charging C is determined by the product R2 C, and sincethis time constant is chosen to be relatively large, the tube V1 maycontinue to conduct for three or four seconds, for example, after theopening of swi ch S1. It the switch S1 is re-closed during this intervalthe controlled device I I will not be de-actuated during the open periodof switch S1. Thus, with a temporary failure of power which is quicklyresumed, the controlled device II will not be deenergized.

Although the invention has been described with respect to a preferredembodiment thereof, it is not to be so limited as changes andmodifications may be made therein which are within the full intendedscope of the invention as defined by th appended claims.

I claim:

1. Control means for a controlled device comprising, a first electronicvalve which has its plate connected in series with the controlled device to a positive direct current voltage and its cathode connected inseries with a first resistor to ground, a second electronic valve withits plate connected to ground and its cathode con nected to the grid ofthe first electronic valve, the grid of the first electronic valveconnected to one side of a condenser which has its opposite sideconnected to ground, a grid leak resistor connected between the grid andcathode of the second electronic valve, a voltage divider comprisingthird and fourth resistors connected in series between ground and anegative direct cur rent voltage, the grid of the second electronicvalve connected to the connection point between said third and fourthresistors, and switching means for connecting said connection point toground.

2. Control means for obtaining a fast attack time and a slow releasetime in a controlled device comprising, a first electron valve with thecontrolled device connected in its plate circuit in series with apositive direct current voltage, a second electron valve with itscathode con nected to the grid of the first electron valve, a capacitorconnected to the cathode of the second electron valve and its oppositeside connected to ground, a grid leak resistor connected between thegrid of the second electron valve and the cathode, a voltage dividercomprising a pair of resistors connected in series between ground and anegative direct current voltage, the grid of said second electron valveconnected to the mid-point between said first and second pair ofresistors, a controlling switch connected to ground and movable toconnect the mid-point between the pair of resistors to ground.

3. A control circuit for instantaneously energizing a controlled deviceand de-energizing said controlled device only after a pro-determinedtime comprising, a first electron valve with its plate connected inseries with said controlled device to a positive direct current voltage,a first resistor connected between ground and the oathode of the firstelectron valve, a second electron valve with its plate connected toground and its cathode connected to the grid of the first electronvalve, a capacitor connected to the cathode of said second electronvalve and its opposite side connected to ground, a second resistorconnected between the grid and cathode of the second electron valve,third and fourth resistors connected in series between a negative directcurrent voltage and ground, the grid of the second electron valveconnected to the junction between the third and fourth resistors, andswitching means with a movable throw arm connected to ground and movableto engage the junction point between the third and fourth resistors.

4. A control device with a fast attack time and a slow release time fora controlled device comprising, a first electron valve, a secondelectron valve with its cathode connected to the control grid of thefirst electron valve, a charging circuit comprising a resistor andcondenserconnected to the cathode of said second electron valve, avoltage divider comprising a pair of resistors connected between anegative direct current voltage and ground, the grid of said secondelectron valve connected to said voltage divider, switching means forconnecting the mid-point between said pair of resistors to ground, andsaid first and second electron valves having minimum current when saidswitching means is open and maximum conduction when said switch isclosed.

JOHN W. SMITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,277,098 Haines Mar. 24, 19422,503,835 Montgomery Apr. 11, 1950

